Sublingual Immunotherapy (SLIT): What is it and when will it be available?

Sublingual Immunotherapy (SLIT) is a type of desensitization for allergies where the substances causing allergies (allergens) are placed under the tongue and then swallowed. Some people think of this as placing allergy drops under the tongue. SLIT is currently licensed for use in several European countries, but it is not licensed for use in the U.S. Drug trials have been completed in the U.S. but they did not show a statistically significant benefit over placebo. My office was and is fortunate to be a participant in these studies, through our research department ADAC Research. The manufacturing companies have not given up and have scheduled more trials in the U.S. Stay tuned for details about our next study or check.

Several important questions regarding its use have yet to be answered, to the satisfaction of the F.D.A. and from me. What is the optimal maintenace dose of the allergy extracts? How long should SLIT be given to get the maximum benefit? What is SLIT's long term safety and efficacy? Studies have been completed but they show mixed results. For example, an European study of grass pollen extracts given using SLIT after two years followup showed no benefit (Roder et al 2007). Which allergens can be mixed together safely and with benefit? No combination studies have been done. Benefit has been shown for inidividual allergens: trees, grasses, and dust mites.

I attended the American College of Allergy, Asthma and Immunology's international meeting in Seattle 11/7-12/08. (I was one of perhaps three allergists from South Carolina and the only allergist from the entire Upstate region.) I had an opportunity to listen to and interact with some of the leading researchers in the U.S. during the plenary sessions. This was very stimulating intellectually. I also got to speak with the manufacturers. My impression is that eventually SLIT will be approved in the U.S. Given the current data, I predict SLIT will not be available in the U.S. for at least 3 more years.